Cartridge fuse and switchgear incorporating the fuse



p 1943- K. DANNENBERG 2,330,690

CARTRIDGE FUSEAND SWITCHGEAR INCORPORATING THE FUS E Filed Jan. 25, 1941Patented Sept. 28, 1943 CARTRIDGE FUSE AND SWITCHGEAR IN CORPORATIN GTHE FUSE Kurt Dannenberg, Islington, London, England, assignor ofone-half to Electric Transmission Limited, Etruria, S shire, Englandtoke-on-Trent, Stafford- Application January 25,1941, Serial No. 375,99!In Great Britain May 31, 1940 25 Claims.

This invention has reference to improvements in and relating tocartridge fuses, i. e., fuses in the form of hermetically closed, powderfilled sheaths containing fusible elements, for high, low and mediumvoltages.

According to one feature of the invention a trip hammer which isarranged to be displaced with sufficient force to cause it mechanicallyto open an electric switch is held against return movement by a lockingdevice arranged to engage with it after it has been so displaced. Thehammer has a part which is permanently exposed (i. e., exposed even whenthe fuse is not blown and is in service condition) to permit of easyaccess to the hammer.

Another feature of the invention comprises switchgear having athree-phase switch and fuses in accordance with the foregoing in serieswith the phases of the switch with their hammers, which act as strikers,commonly associated with the opening member of the switch so thatoperation of any fuse opens all switch phases and prevents closing ofthe switch until such time as an intact fuse i. e., a fuse fit forservice) replaces the operated fuse in the switchgear.

One form of fuse, a detail in connection with the mounting of fusibleelements therein, an alternative form of hammer locking device and athree-phase switch according to the invention will now be described withreference to the accompanying drawing wherein:

Fig. 1 is a side elevation of a medium voltage fuse with that endthereof having the trip hammer shown in section;

Fig. 2 is a view of the trip hammer end of the fuse after removal of theconnecting tag at this end;

Fig. 3 is a face view of a notched ring for supporting a number offusible elements;

Fig. 4 is an end view of a connecting tag on which a spring-drivenlocking bit is mounted; and

Fig. 5 is a diagrammatically shown switchgear comprising a three-phaseswitch and three fuses with permanently accessible trip hammers.

The fuse illustrated in Figs. 1 and 2 comprises the usual refractory,insulating sheath l with internally flanged caps 2 secured to it at itsends. Screw-threaded sockets 3 are sunk into the ends of the sheath totake fixing screws 4 which secure the connecting tags 5 and 5, discs 6and 6 and intermediate rings 1, 1 and 8, B to the sheath. The elements6, I and 8, and 6, 1'. 8, are of metal and each set thereof is firmlyclamped between its adjacent connecting tag and end of the sheath by thescrews 4.

The ring 8 has an inwardly directed tongue 9 to which a cylinder III forthe trip hammer I l is welded near the inner end of the tongue, thecylinder l0 extending inwardly of the sheath l.

The disc 6 has a diamond-shaped slot l2, the centre of which coincideswith the axis of the trip hammer II; and the ring I has an inwardlydirected tongue l3 which lies against one side of the slot. Thecorresponding connecting tag 5 lies against the other side of the saidslot. In this manner a shallow chamber is provided.

The outer end of the trip hammer extends through holes l4 and IS in thetongues 9 and I3. respectively, through the middle portion of the saidchamber and through a hole IS in the tag 5.

Within the said chamber are two bowed wire springs l! which tendnormally to close towards each other but are prevented from doing so bycontact with the sides of the hammer l I.

The cylinder in extends well beyond the inner end of the hammer II toprovide a chamber I8 for explosive powder (e. g. gunpowder) IS.

The hammer is annularly grooved at 20 near its inner end and one end ofthe fusible element 2| is connected to the hammer, said element passingthrough an insulating bush 22 on the closed end of the cylinder Ill andthrough the explosive chamber i8.

When the element 2| fuses it ignites the powder I9 and the hammer I l isejected until the groove 20 comes into register with the springs l1whereupon the said springs close into the groove and lock the hammeragainst both forward and backward movement.

The outer end of the hammer has a screwthreaded shank 23 enablingit tobe connected to or associated with a switch; and that portion of thehammer H normally within the hole I6 is squared and the said hole is ofcorresponding shape to prevent rotation of the hammer when a connectingbody is applied to the shank.

The element 2| is of coil form to enable the requisite length of wire tobe arranged in the sheath having the length shown, in spite of thecylinder l0 projecting well into the sheath. The coil and the cylinderare substantially aligned.

A second fusible element 24 electrically parallel with 2| is locatedwithin the sheath; its ends are connected to the rings 8 and it isstretched between the inner peripheries of two ceramic rings or supports25 let into recesses at the ends of the sheath.

The fuse is filled with powder indicated by 26 and the sealing providedby the members screwed to the ends of the sheath is such as to behermetic or nearly so.

The element 2|, which is the main interruption element, preferablyconsists of tungsten and is so graded with respect to the explosivecharge that approximately sec. time is required for the hammer tocomplete its ejection stroke. Thus, the said element dissipates insidethe fuse before the hammer fully operates.

When it is desired to provide a fuse of high current rating the rings 25are replaced by rings as 21 illustrated in Fig. 3. The rings 21 havearcuate slots 28 around the bore 29 and the inner peripheral portions ofthe slots and of the bore are recessed at 30. Elements additional to thecoil 2| and electrically parallel therewith have their ends secured tothe rings 8 and stretch from ring to ring with those portions contactingwith the rings lying in the recesses 30.

Instead of employing springs H to lock the hammer I I I may use thespring-driven bit 3i, Fig. 4. This is mounted on the tag and it normallypresses against the outer end of the hammer and, when the fuse operates,enters the groove 20, owing to the action of the blade spring 32.

The switchgear illustrated in Fig. 5 comprises the three-phase switch 33and three fuses 34 having permanently accessible hammers. Each fuse isin series with a phase of the switch and the hammers have insulated ends35 adjacent to arms 36 rigid with the operating rod 31 of the trip 38 cfthe switch. Thus, operation of any one fuse causes its hammer partiallyto turn the shaft 31 and this upsets the trip to cause all phases of theswitch to be opened. When the switch is so opened the trip is held inthe upset position owing to the locking of the operated hammer and'cannot be reset until such time as an intact fuse is substituted for theone that has operated. The switch 33 and its trip may be of any suitableknown kind. Alternatively, the switch may be of the type which isdirectly opened by the turning of a shaft.

Part of one of the hammers in Fig. 5 is in section. The hammer has ascrew-threaded bore 39 into which a metal shank 40 on the insulating end35 fits.

What I claim is:

l. A cartridge fuse comprising a refractory, insulating sheath, afusible element in said sheath, an arc-extinguishing powder filling insaid sheath, hermetic closures at the ends of the sheath, a trip hammermounted on said fuse, means activated by the fusing of the fusibleelement adapted to displace the trip hammer with a force sufficient tocause it mechanically to open an electric switch, and a locking deviceadapted to hold said hammer against return movement after it has been sodisplaced.

2. A cartridge fuse comprising a refractory, insulating sheath, afusible element in said sheath, an arc-extinguishing powder filling insaid sheath, hermetic closures at the ends of the sheath, a trip hammermounted on said fuse, said hammer having a part which is permanentlyexposed topermit of easy access to it even when the fuse is not blownand is in service condition, means activated by the fusing of thefusible element adapted to displace the trip hammer with a forcesufiicient to cause it mechanically to open an electric switch, and alooking device adapted to hold said hammer against return movement a terit has been o di m 3. A cartridge fuse comprising a refractory,insulating sheath, a fusible element in said sheath, anarc-extinguishing powder filling in said sheath, hermetic closures at.the ends of the sheath, a trip hammer mounted on said fuse, a shankextending from said hammer, said shank being exposed to permit of easyaccess to it even when the fuse is not blown and is ,in servicecondition, means activated by the fusing of the fusible element adaptedto displace the trip hammer with a force sufficient to cause itmechanically to open an electric switch, and a locking device adapted tohold said hammer against return movement after it has been so displaced.

4. A cartridge fuse comprising a refractory, insulating sheath, afusible element in said sheath, an arc-extinguishing powder filling insaid sheath, hermetic closures at the ends of the sheath, a trip hammermounted on said fuse, said hammer having a screw-threaded bore which ispermanently exposed to permit of easy access to it even when the fuse isnot blown and is in service condition, means activated by the fusing ofthe fusible element adapted to displace the trip hammer with a forcesufiicient to cause it mechanically to open an electric switch, and alocking device adapted to hold said hammer against return movement afterit has been so displaced.

5. A cartridge fuse comprising a refractory, insulating sheath, afusible element in said sheath, an arc-extinguishing powder filling insaid sheath, hermetic closures at the ends of the sheath, a trip hammermounted on said fuse, said hammer having a groove, means activated bythe fusing of the fusible element adapted to displace the trip hammerwith a force sufficient to cause it mechanically to open an electricswitch, and a spring locking device adapted to engage with said grooveto hold the hammer against return movement after it has been sodisplaced.

6. A cartridge fuse comprising a refractory, insulating sheath, afusible element in said sheath, an arc-extinguishing powder filling insaid sheath, hermetic closures at the ends of the sheath, a trip hammermounted on said fuse, said hammer having a groove, means activated bythe fusing of the fusible element adapted to displace the trip hammerwith a force sufilcient to cause it mechanically to open an electricswitch, a flat body at one end of said sheath, a second fiat body lyingagainst said first body and a third fiat body lying against said secondbody, the second body having a slot and the first and third bodieshaving openings of smaller size than the slot whereby a chamber isprovided, and a spring locking device in said chamber, the trip hammerextending through said openings and said chamber and said spring devicebeing arranged to engage with the groove in the trip hammer to hold saidhammer against return movement after it has been displaced subsequentlyto fusing of the fusible element.

7. A cartridge fuse comprising a refractory, insulating sheath, afusible element in said sheath, an arc-extinguishing powder filling insaid sheath, hermetic closures at the ends of the sheath, a trip hammermounted on saidfuse, said hammer having a groove, means activated by thefusing of the fusible element adapted to displace the trip hammer with aforce sufficient to cause it mechanically to open an electric switch,connecting tags at the ends of the fuse and a spring locking devicemounted on one of said tags arranged to engage with the groove in thetrip hammer to hold said hammer against return movement after it hasbeen displaced subsequently to fusing of the fusible element.

8. A cartridge fuse comprising a refractory, insulating sheath, afusible element in said sheath, an arc-extinguishing powder filling insaid sheath, hermetic closures at the ends of the sheath, a trip hammermounted on said fuse, said hammer and said fusible element being inseries electrically, means activated by the fusing of the fusibleelement adapted to displace the trip hammer with a force sumcient tocause it mechanically to open an electric switch, and a locking deviceadapted to hold said hammer against return movement after it has been sodisplaced.

9. A cartridge fuse comprising a refractory, insulating sheath, anhelically coiled fusible element in said sheath, an arc-extinguishingpowder filling in said sheath, hermetic closures at the ends of thesheath, a cylinder located at one of said ends coaxially of the coiledfusible element, said cylinder extending into the sheath, a trip hammerlocated in said cylinder and connected in series electrically with saidfusible element, means activated by the fusing of the fusible elementadapted to displace the trip hammer with a force sufficient to cause itmechanically to open an electric switch, and a locking device adapted tohold said hammer against return movement after it has been so displaced.

10. A cartridge fuse comprising a refractory, insulating sheath, anhelically coiled fusible element in said sheath, an arc-extinguishingpowder filling in said sheath, hermetic closures at the ends of thesheath, a cylinder located at one of said ends coaxially of the coiledfusible'element, said cylinder extending into the sheath, an explosivepowder in the cylinder traversed by the fusible element, and a triphammer in the cylinder, ignition of the powder as a result of theelement fusing effecting displacement of the trip hammer with a forcesuflicient to cause it mechanically to open an electric switch, and alocking device adapted to hold said hammer against return movement afterit has been so displaced.

11. In a cartridge fuse according to claim 9, insulating rings near theends of the cartridge, said rings having longitudinal openings in themat different distances from their centers, the openings in one ringcorresponding with those in the other and said rings surrounding theaxis of the coiled fusible element and being parallel with the ends ofthe cartridge, terminal rings adjacent to said insulating rings, saidterminal rings surrounding the axis of the coiled fusible element, andmain service elements, said main service elements being electricallyparallel with each other and with said coiled fusible element andstretching from openings in one insulating ring to correspondingopenings in the other ring and connected at their ends to said terminalrings whereby said main service elements are of different length owingto the position of the holes in the insulating rings with relation tothe terminal rings and, therefore, said elements of different lengthdissipate in steps when the fuse efiects an electrical interruption.

12. In a cartridge fuse according to claim 9, insulating rings near theends of the cartridge, said rings having longitudinal openings in themat different distances from their centers, the openings in one ringcorresponding with those in the other and the sides of said openingshavwith each other and with said coiled fusible element and stretchingfrom openings in one insulating ring to corresponding openings in theother insulating ring and lying in said notches and connected at theirends to said terminal rings whereby said main service elements are ofdifferent length owing to the position of the holes in the insulatingrings with relation to the terminal rings and, therefore, said elementsof different length dissipate in steps when the fuse effects anelectrical interruption.

13. A cartridge fuse, comprising a refractory insulating sheath, afusible element in said sheath, an arc-extinguishing powder filling insaid sheath, hermetic closures at the ends of the sheath, a trip hammermounted on said fuse, said hammer having a part which is permanentlyexposed to permit of easy access to it even when the fuse is not blownand is in service condition, and means activated by the fusing of thefusible element adapted to displace the trip hammer with a forcesufficient to cause it mechanically to open an electric switch,

14. A cartridge .fuse, comprising a refractory insulating sheath, afusible element in said sheath, an arc-extinguishing powder filling insaid sheath, hermetic closures at the ends of the sheath, a trip hammermounted on said fuse, a shank extending from said hammer, said shankbeing exposed to permit of easy access to it even when the fuse is notblown and is in service condition, and means activated by the fusing ofthe fusible element adapted to displace the trip hammer with a forcesufficient to cause it mechanically to open an electric switch.

15. A cartridge fuse comprising a refractory insulating sheath, afusible element in said sheath, an arc-extinguishing powder filling insaid sheath, hermetic closures at the ends of the sheath, a trip hammermounted on said fuse, said hammer having a screw threaded bore which ispermanently exposed to permit of easy access to it even when the fuse isnot; blown and is in service condition, and means activated by thefusing of the fusible element adapted to displace the trip hammer with aforce sufficient to cause it mechanically to open an electric switch.

16. A cartridge fuse, comprising a refractory insulating sheath, afusible element in said sheath, an arc-extinguishing powder filling insaid sheath, hermetic closures at the ends of the sheath, a trip hammermounted on said fuse, said hammer and said fusible element being inseries electrically, and means activated by the fusing of the fusibleelement adapted to displace the trip hammer with a force sufficient tocause it mechanically to open an electric switch.

17. A cartridge fuse, comprising a refractory insulating sheath, anhelically coiled fusible element in said sheath, an arc-extinguishingpowder filling in said sheath, hermetic closures at the ends of thesheath, a cylinder located at one of said ends coaxially of the coiledfusible element, said cylinder extending into the sheath, a trip hammerlocated in said cylinder and connected in series electrically with saidfusible element, and means activated by the fusing of the fusibleelement adapted to displace the trip hammer with a force suflicient tocause it mechanically to open an electric switch.

18. A cartridge fuse, comprising a refractory insulating sheath, anhelically coiled fusible element in said sheath, an arc-extinguishingpowder filling in said sheath, hermetic closures at the ends of thesheath, a cylinder located at one of I said ends coaxially of the coiledfusible element, said cylinder extending into the sheath, an explosivepowder in the cylinder traversed by the fusible element, and a triphammer in the cylinder, ignition of the powder as a result of theelement fusing elfecting displacement of the trip hammer with a forcesufiicient to cause it me chanically to open an electric switch.

19. In a cartridge fuse according to claim 9,

wherein the trip hammer is provided with a per said main serviceelements being electrically parallel with each other and with saidcoiled fusible element and stretching from openings in one insulatingring to corresponding openings in the other ring and connected at theirends to said terminal rings, whereby said main service elements are ofdifferent length owing to the position of the holes in the insulatingrings with relation to the terminal rings, and therefor e said elementsof different length dissipate in steps when the fuse effects anelectrical interruption.

20, In a cartridge fuse according to claim 9, wherein the trip hammer isprovided with a permanently accessible part, and wherein there isprovided insulating rings near the ends of the cartridge, said ringshaving longitudinal openings in them at different distances from theircenters, the openings in one ring corresponding with those in the otherand the sides of said openings having notches in them and said ringssurrounding the axis of the coiled fusible element and being parallelwith the ends of the cartridge, terminal rings adjacent to saidinsulating rings, said terminal rings surrounding the axis of the coiledfusible element, and main service elements, said main service elementsbeing electrically parallel with each other and with said coiled fusibleelement and stretching from openings in one insulating ring tocorresponding openings in the other insulating ring and lying in saidnotches and connected at their ends to said terminal rings, whereby saidmain service elements are of different length owing to the position ofthe holes in the insulating rings with relation to the terminal rings,and therefore said elements of different length dissipate in steps whenthe fuse effects an electrical interruption.

21. A cartridge fuse, comprising a refractory insulating sheath, a mainservice fusible element in said sheath and a main interruption elementin said sheath, an arc-extinguishing powder filling in said sheath, saidmain service and main interruption elements being embedded in saidpowder filling, an explosive container in said sheath, an explosive insaid container, said main interruption element entering said containerto make igniting relationship with said explosive 5 upon cut-outoperation of the fuse, and a trip hammer mounted on said fuse, said triphammer being located between said explosive and atmosphere and saidexplosive being present in sufficient quantity to ensure that when themain interruption element ignites it the trip hammer is displaced with aforce sufficient to enable it mechanically to open an electric switch,and a locking device to hold said hammer against return movement afterit has been displaced by the explosive charge.

22. A construction as defined in claim 21, wherein the trip hammer isprovided with a permanently accessible part.

23. A cartridge fuse, comprising a refractory insulating sheath, afusible element in said sheath, an arc-extinguishing powder filling insaid sheath, hermetic closures at the ends of the sheath, a trip hammermounted on said fuse, said hammer having a part which is permanentlyexposed to permit of easy access to it even when the fuse is not blownand is in service condition and said hammer and said fusible elementbeing in series electrically and being mechanically continuous with eachother, means adapted to 30 hold said trip hammer against rotation withrespect to said cartridge fuse, and means activated by the fusing of thefusible element adapted to displace the trip hammer forcibly.

24. A cartridge fuse, comprising a refractory 35 insulating sheath, afusible element in said sheath, an arc-extinguishing powder filling insaid sheath, hermetic closures at the ends of the sheath, a trip hammermounted on said fuse, said hammer having a part which is permanentlyexposed to permit of easy access to it even when the fuse is not blownand is in service condition and said hammer and said fusible elementbeing'in series electrically and being mechanically continuous with eachother, means adapted to hold said trip hammer against rotation withrespect to said cartridge fuse, means activated by the fusing of thefusible element adapted to displace the trip hammer forcibly, andalocking device adapted to hold said hammer against return movementafter it has been so displaced.

25. A cartridge fuse, comprising a refractory insulating sheath, anhelically coiled fusible element in said sheath, an arc-extinguishingpowder filling in said sheath, hermetic closures at the ends of thesheath, a cylinder located at one of said ends coaxially of the coiledfusible element, said cylinder extending into the sheath, an explosivepowder in the cylinder traversed by the fusible element, a trip hammerin the cylinder, said trip hammer having a part which is permanentlyexposed to permit of easy access to it even when the fuse is not blownand is in service condition and said fusible element and said triphammer being in series electrically and being mechanically continuous,ignition of the powder as a result of the element fusing effectingforcible displacement of the trip hammer, and means preventing rotationof said trip hammer with respect to said fusible element.

KURT DANNENBERG.

